Silk

Silk is a free-to-play item on the OSRS Grand Exchange in the other category.

In-game examine text: "It's a sheet of silk."

It has a Grand Exchange buy limit of 18,000 every four hours, a high alchemy value of 18 gp, and item ID 950.

View on OSRS Wiki

Silk shows an active flip setup with a margin of +2 gp and 26,199 trades over the last 24 hours.

At the buy limit of 18,000 every four hours, max profit per cycle is about 36.0k gp — high margin with healthy liquidity.